Grinding units with a variety of different mill types are already known. They consist of a product feed unit, mill, product collection unit and fan. Some products require a high air flow rate to cool the product during grinding, these types of systems are operated in through-air mode. Other products are less temperature-sensitive and can be processed without a separate flow of cooling air. To aid transport of these products, the air can be circulated. The advantage of this solution is that elaborate product collection units such as cyclones or filters are not necessary.
German Patent DE 9300910 U1 describes a system for grinding sugar. In this instance, a mill is top-mounted directly on a container. The ground product is routed via this collection hopper to the discharge. In this example, the air is circulated through the mill, whereby the air from the collection hopper is extracted and supplied to the product inlet upstream of the mill.
Despite this device, improvements are still desirable, and these are now provided by the present invention.